This invention relates to cooling of turbine rotor disks and blades of gas turbine engines with injection of cooling air onto a rotating turbine disk assembly and, in particular, to retention of a disk side plate on the side of a disk of the disk assembly.
In gas turbine engines, fuel is burned within a combustion chamber to produce hot gases of combustion. The gases are expanded within a turbine section producing a gas stream across alternating rows of stationary stator vanes and turbine rotor blades to produce usable power. Gas stream temperatures at the initial rows of vanes and blades commonly exceed 2,000 degrees Fahrenheit. Blades and vanes, susceptible to damage by the hot gas stream, are cooled by air compressed upstream within the engine and flowed to the turbine components. One technique for cooling rotating turbine disk assemblies, having blades attached to rims of disks, injects cooling air from stationary cavities within the engine to a disk assembly for distribution to the interior of the turbine blades. A cooling air injection nozzle is a well-known device used to receive compressed air from a compressor of the engine and inject the cooling air through circumferentially spaced passages that impart a swirling movement and directs an injected stream of the cooling air tangentially to the rotating turbine disk assembly. A typical turbine disk assembly has the turbine blades attached to the rims of the disk and a disk side plate attached to a forward or aft face of the disk forming a cooling air passage between the plate and the disk. Circumferentially spaced vanes on the disk side plate that extend radially from a radially inner position on the disk to the radially outer rim and root of the blades may be used to form individual passages between the plate and disk.
The plate also is used to axially retain the blades in dovetail slots in the rim of the disk and to support one or more rotating seals. In order to perform these functions, the disk side plate is usually restrained axially and supported radially by the disk out near the rim or on the web, where the stress fields are typically high. In the case where a disk side plate supports inner and outer rotating seals, or where the outer section of the disk side plate requires more radial support, a means of axial retention and radial support may be required at a lower radially inner position of the disk also. One commonly used disk side plate restraint is a bayonet mount. A bayonet mount design requires an interrupted cut in a bayonet arm of the disk so the disk side plate and disk may mesh and provide axial and radial retention of the plate. These interruptions in the arm, especially in the disk where the hoop and radial stress fields are high, provide 3D stress risers that frequently result in the life limiting areas on both the disk and disk side plate. These 3D features are geometrically complicated and so are also difficult to analyze and life. Even without these interruptions, however, the disk bayonet arm has a fillet that forms an abrupt change in cross-sectional thickness that provides a 2D radial stress riser. Typically, there is also a variable radial rabbet load included in the bayonet feature that complicates the analysis and design. The typical bayonet feature complicates the analysis and design and the typical bayonet arm retention design usually results in a few potential life-limiting locations. In addition to the life limiting concerns, the bayonet feature is typically difficult and expensive to machine. A bayonet arm pocket usually requires special tooling to machine and is difficult to inspect for flaws. This feature is also a common cause of part scraping.
Another low radius disk side plate retention well known in the art is a bolted joint which provides satisfactory part retention, but results in a heavy, bulky configuration with a high parts count. In addition, since bolt sizes don""t scale down with engine size, small gas generators usually don""t have the space for a joint like this.
An annular disk side plate includes an annular plate hub and an annular plate shaft extension extending axially forwardly from the plate hub. A plate web extends radially outwardly from the plate hub and a plate rim extends radially outwardly from the plate web. In the exemplary embodiments of the invention illustrated herein, the plate rim is canted aftwardly from the plate web. One or more axially extending annular sealing ridges (in the exemplary embodiment of the invention illustrated herein, there are two sealing ridges) extend aftwardly from the plate rim to seal against a disk with which the plate is designed to mate. An annular groove is disposed a radially inwardly one of the sealing ridges and a sealing ring or sealing wire is disposed within the annular groove to seal against the disk. The side plate further includes an anti-rotation means for preventing rotation of the disk side plate relative to the disk. The anti-rotation means includes elements located on the plate shaft extension which are exemplified by a circumferential row of radially extending circumferentially spaced apart tabs. Cooling air apertures or holes are disposed through the plate web of the side plate and extend axially through the plate web. The disk side plate further includes a radially inner most inner cylindrical surface of the plate shaft extension and an outer cylindrical surface of the plate shaft extension that is spaced radially outwardly of the inner cylindrical surface. The annular disk side plate has a recess extending axially aftwardly into the plate hub and has a radially outer rabbet joint corner. A radially outwardly extending annular ridge is located directly between the plate shaft extension and the recess and traps a sealing wire between the plate shaft extension an annular disk shaft extension of an annular rotor disk.
The present invention includes a rotor assembly with the annular rotor disk comprising a disk hub and the annular disk shaft extension extending axially forward from the disk hub. A disk web extends radially outwardly from the disk hub and a disk rim extends radially outwardly from the disk web. A plurality of rotor blades are mounted in and extend radially outwardly from the disk rim and the disk rim has a forward facing seal face on the disk rim. The annular disk side plate is mounted on an annular forward facing side of the disk and the plate shaft extension is mounted on the disk shaft extension. The cooling air holes disposed through the side plate lead to annular radial passages between the disk side plate and the disk and which conveys cooling air to inlets that lead to the rotor blades. Optionally, cooling plate vanes (not illustrated) on the disk side plate may be used. The cooling plate vanes extend radially outwardly forming circumferentially spaced apart walls of the radial passages. A pre-loading means for pre-loading the side plate in compression against disk seals, the annular sealing ridges against the seal face by axially securing the plate shaft extension to the disk shaft extension.
A first exemplary pre-loading means includes an annular groove in a radially outer surface of the disk shaft extension and a ring disposed in the groove such that the ring axially engages the groove and the plate shaft extension. The ring axially engages an aftwardly facing surface of the groove and axially engages a forwardly facing surface of the plate shaft extension. An exemplary anti-rotation means is disposed on the plate and disk shaft extensions and includes a plurality of first tabs depending radially inwardly from and circumferentially disposed around the plate shaft extension. In the exemplary embodiment illustrated herein, the first tabs depend radially inwardly from a pilot located at a forward end of the plate shaft extension. The anti-rotation means further includes a plurality of second tabs depending radially outwardly from and circumferentially disposed around the disk shaft extension and having first tab spaces between the first tabs and second tab spaces between the second tabs. The first and second tabs are circumferentially interdigitated such that the first tabs are disposed in the second tab spaces and the second tabs are disposed in the first tab spaces. An annular collar member is circumferentially disposed around the plate shaft extension and has a radially inwardly depending flange forming an annular corner around the ring disposed in the groove. A radially outwardly extending annular flange at an aft end of the annular collar member is disposed in the recess forming a rabbet joint with the radially outer rabbet joint corner. In the exemplary embodiment of the invention, the annular collar member is a seal runner having one or more one annular seal lands disposed around the seal runner.
In a second exemplary rotor assembly, the pre-loading means includes the plurality of first tabs depending radially inwardly from and circumferentially disposed around the plate shaft extension and the plurality of second tabs depending radially outwardly from and circumferentially disposed around the disk shaft extension. The first tab spaces are disposed between the first tabs and the second tab spaces are disposed between the second tabs. The first and second tabs are circumferentially aligned and loaded in compression against each other. The anti-rotation means includes a plurality of axially extending third tabs wherein each of the third tabs is disposed in the first and second tab spaces between adjacent ones of the first tabs and between adjacent ones of the second tabs. The anti-rotation means further includes the annular collar member circumferentially disposed around the plate shaft extension and the third tabs depend radially inwardly from the collar member.